Rio de Janeiro boasts the world's最大水处理厂，并且正在加班。圭杜水处理站提供了里约市90％的水，并且越来越多地应对水质问题。一个挑战是，城市上游的森林丧失和景观退化正在引起土壤侵蚀，这会产生更多的污染，并用沉积物代替水充满水库。这会导致昂贵的水处理和疏gried需求。

一项创新的策略，以经济有效地处理这种水污染，超越了城市的处理厂并进入其周围的森林。一种new WRI studyfinds that restoring more forests around Rio could save the city up to $79 million in water treatment costs, while dramatically reducing the amount of chemicals used to treat drinking water.

森林过滤水并降低城市的水处理成本

Trees naturally filter the water that runs through them, providing cleaner water to people downstream and reducing water treatment costs. Forests also protect cities from floods and landslides, and reduce wear and tear on downstream built infrastructure like dams and treatment plants.

向900万人供水给圭杜治疗厂施加了巨大压力。由于水的数量移动，即使是少量污染也可能导致高昂的成本。挑战正在加剧 - 要满足2030年城市的需求，经过处理的水的供应可能需要增加高达50％。里约热内卢也面临预算危机。越来越多地花在水处理上对这座城市没有好处。

Rio's water managers are already experimenting with using forest protection and other "natural infrastructure" for cleaner water. The water utility, CEDAE, through its ongoing "Replanting Life" program has been restoring riverside areas and protecting springs. The local hydropower company, LIGHT, has reforested approximately 600 hectares of land since 1992. The Water and Forest Producer Program, primarily funded by the Guandu Watershed Committee, has already raised over $3 million for natural infrastructure efforts like reforesting important areas of the river basin and protecting standing native forest.

这些小规模的努力值得称赞，但不足以孤立 - 由于里约不断增长的预算危机，他们承受着压力。

自然基础设施的成本效益分析

WRI's new report provides a cost-benefit analysis of natural infrastructure development in Rio, which can help government officials understand and justify investments in forests for water management objectives. We applied our Green-Gray Assessment, a tool that helps water-dependent companies and investors examine the costs and benefits of utilizing green infrastructure in combination with traditional, built infrastructure.

我们发现，在里约热内卢的有针对性地点恢复3,000公顷的本地森林将需要大约2640万美元的初始投资，但在30年内避免了7,900万美元的成本，即每年260万美元。在未来30年内，投资于森林还将避免使用估计的400万吨化学产品和260MWH的能源。

The price tag of over $26 million to restore forests may seem high to some. But, importantly for cash-strapped states like Rio de Janeiro, natural infrastructure does not necessarily require additional financial resources—rather, it may involve rerouting existing funds and aligning with other efforts already funding landscape restoration. Because natural infrastructure can do much more than purify water, it can also attract investors interested in reducing carbon emissions, boosting rural livelihoods or protecting biodiversity.

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里约圭杜河盆地的森林。照片由Marcelo Matsumoto/Wri Brasil摄

Should Other Cities Pursue Natural Infrastructure for Water?

This report is the second in a series of studies on natural infrastructure for water in Brazil and Mexico. Thefirst reportassessed water supply in São Paulo and found that restoring 4,000 hectares of forest could generate cost savings of $106 million for the local water company.

Other cities around the world are grappling with the same kinds of water problems as São Paulo and Rio. Byone estimate，分水岭的退化影响了超过7亿人的饮用水质量，并且每年最大的城市耗资54亿美元的水处理。WRI的绿色灰色评估可以应用于任何流域。当自然基础设施项目考虑到本地环境时，它们可以帮助世界各地的许多地方提供清洁的水。

该报告是由Boticário集团自然保护和自然保护基金会（TNC）与FEMSA基金会，国际自然保护联盟（IUCN），ICNITUTOBIOATLântica（IBIO）（IBIO）和自然资本项目合作的WRI开发的。有关我们的研究和方法的更多信息，请参阅报告，Rio de Janeiro的Infraestrutura NaturalParaáguano Sistema Guandu.